In order to increase the life of oil or grease lubricated rotating systems that are operated at high temperatures, high speeds, and/or high loads, various additives and thickeners are sometimes added to the bearing lubricants.
It has been found, for example, that some compounds that have a lattice structure are good additives for lubricants. These include the selenides and sulfides of tungsten, molybedenum, tantalum, and nioboium. However, it has also been found that compounds that are chemically similar and that also have a lattice structure have a very poor lubricating ability. For example, tellurium is chemically very similar to selenium, but the tellurides of tungsten, molybdenum, tantalum, and niobium are very poor lubricants. Other compounds that have a lattice structure, such as calcium fluoride, are also poor lubricants at temperatures less than about 600.degree. F. Titanium sulfide, which also has a lattice structure, is actually abrasive. Thus, it is difficult to predict from the chemical structure alone whether or not a compound that has a lattice structure will actually perform well as a lubricant.
It is highly desirable that additives in liquid lubricants be somewhat soluble in aqueous, organic or synthetic lubricants. Solid lubricant additives, such as molybdenum disulfide, are substantially more dense than that of the lubricant and thus are substantially insoluble with certain of the liquid lubricants. At turning gear speeds, the shafts of large turbine generators are not rotating at a speed sufficient to support an oil film, or hydrodynamic lubrication of the journal bearings. Thus, there is needed a composition that retains its lubricity under such a "lubricant starved" operating condition.
There remains a need for a lubricant additive with increased solubility in an organic or synthetic lubricant in order to increase the life of the lubricated mechanism.